Camera modules are being applied to mobile phones and Internet cameras with ever-increasing pixel counts and functionality. The improvement in pixel count and functionality is pushed by the progressively increasing pixel counts in CCD and CMOS sensor devices. Large counts of pixels are achieved by reducing the size of pixels in the sensor device. This leads to improvement in the optical mechanism, such as resolution, brightness, and auto focus and zoom functions.
Demand for mobile phones is increasing every year. A huge number of camera modules (tens to hundreds of thousands of units per month and model) is manufactured for application in mobile phones. We cannot disregard this high volume in the manufacture of camera modules. Important factors in achieving the high production volume are how to reduce the step count for easy assembly (to reduce production time) and how to reduce defective modules.
A camera module, manufactured by assembling a solid image capture element and other components, is tested before shipping. An analysis of defects found in the testing shows that they are often caused by a dark line or stain in the image captured by the camera module. These cases do not involve any malfunctioning of the module. Rather, the unwanted line and stain in the captured image is nothing more than shadow of foreign objects and dust which are present in the optical path between the solid image capture element and the internal lens in the camera module. The foreign objects and dust can come from the resin constituting the camera module housing, abrasion of assembly devices during manufacture, workers involved in manufacture, and various other sources. The line and stain should disappear if the foreign objects and dust are removed from inside the camera module or if the component to which the foreign objects or dust is sticking is replaced.
These facts indicate that approaches to defect-causing foreign objects, as well as ease in assembly, should be given consideration in camera module manufacturing.
Patent document 1, taken as an example, describes a camera module incorporating a solution to foreign objects. FIG. 36 is a plan and a cross-sectional view of a solid image capture device in accordance with patent document 1. In the camera module 400, the solid image capture element 402 has an effective pixel area 403 covered by a transparent member 404. The transparent member 404 prevents foreign objects from reaching the light receiving surface (image sensing plane) of the solid image capture element 402.
Patent document 2 describes another camera module incorporating a solution to foreign objects. FIG. 37 is a cross-sectional view of a camera module 500 in accordance with patent document 2. In the camera module 500, an exposure area 503 of a solid image capture element 502 is covered with a transparent plate 504 in an early stage in assembly to reduce adverse effects of foreign objects. Also, in the camera module 500, a sealing resin 509 seals the solid image capture element 502 and a lens holder 508 accommodating a lens 507.
Patent documents 3 and 4 disclose a camera module which is easy to assemble. FIG. 38 is an exploded oblique view of a camera module in accordance with patent document 3. FIG. 39 is an exploded oblique view of a camera module in accordance with patent document 4. A lens barrel in patent documents 3 and 4 is mounted to a wiring board without adhesive and resin sealing.
Specifically, as shown in FIG. 38, a lens 604 (lens barrel) is secured by screws 606 to a wiring board 601 to which a solid image capture element 602 is mounted in a camera module 600 of patent document 3.
Referring now to FIG. 39, in a camera module 700 of patent document 4, tabs 709 formed on a lens barrel 708 are inserted to holes 703 opened in the wiring board 701. Furthermore, a position determine pins 710 on the lens barrel 708 are inserted to receiving holes 704 opened in the wiring board 701.    Patent Document 1: Japanese Unexamined Patent Publication No. 2004-296453 (Tokukai 2004-296453; Oct. 21, 2004)    Patent Document 2: Japanese Unexamined Patent Publication No. 2006-005211 (Tokukai 2006-005211; Jan. 5, 2006)    Patent Document 3: Japanese Unexamined Patent Publication No. 2004-289572 (Tokukai 2004-289572; Oct. 14, 2004)    Patent Document 4: Japanese Unexamined Patent Publication No. 06-177271/1994 (Tokukaihei 06-177271; Jun. 24, 1994)